This invention relates to tool holders, and in particular to a quick-change holder for attaching drill bits and the like to rotating means, such as hand-held drills and drill presses.
Quick-change tool holders and chucks are well-known in the field of tools, and a variety of different designs have been developed in an attempt to achieve a system whereby different drill bits and the like may be quickly and easily inserted in a respective tool holder or chuck, locked against relative rotation with respect thereto and accurately aligned on a rotary axis of the drill or rotating machine tool. A well-known type of drill chuck with gripping jaws for retaining a tool shank requires a separate chuck key for rotating a sleeve relative to the chuck and thereby adjusting the jaws. However, the dependency of such chucks on separate chuck keys for loosening and tightening substantially impairs their convenience of operation. First of all, the key must be twisted in a receiver for both loosening and tightening the drill chuck, thereby requiring two separate additional operations with the key for changing a drill bit. Secondly, the separate chuck keys are prone to being lost or misplaced, whereby the drill may be rendered substantially inoperative. A third disadvantage with respect to requiring separate keys is that such keys are not necessarily interchangeable between different drill chucks. Finally, maximum effective gripping force on a drill bit is obtained with such chucks by sequentially placing the key in each separate receiver and twisting it whereby each respective gripping jaw is tightened. However, this procedure is frequently not followed and the drill bits are thereby out of alignment with the rotary axis of the drill and subject to slippage, scoring, and inaccurate drilling.
Several quick-change drill chucks have been designed in an attempt to achieve positive attachment of a drill bit to a drill without dependence upon a chuck key. Several of these chucks include collets or adaptors within which the drill bit shank is retained and which are then inserted into a chuck or tool holder attached to a drill or other rotating machine tool. For example, see the Poutie U.S. Pat. No. 2,370,487 wherein a tapered collet receives a drill bit and is tightened thereagainst by a chuck nut threadably engaging the collet. This assembly may then be inserted into an adaptor and retained therein by a ball plunger. However, for quickly changing different sizes of drill bits with such a device a separate collet and chuck nut are required for each drill bit. Also, relative rotation between the drill bit and the adaptor is prevented only by a friction engagement of the drill bit within a slot in the collet.
Keyless chucks have also been developed which utilize gripping elements radially moveable with respect to a drill bit similar to key-type drill chucks. See for example the Vogel U.S. Pat. No. 4,252,333 wherein a control sleeve moves axially with respect to a cylindrical body in response to relative rotation therebetween, whereby gripping elements positioned in a tapered bore tighten or loosen radially with respect to a drill bit shank. However, slippage of the drill bit relative to such a chuck may occur if the gripping elements are not sufficiently tightened. Also, tightening such keyless chucks about respective drill bits is generally more difficult than with key-type chucks wherein the chuck key provides additional leverage for tightening the chuck.
In addition to their aforementioned disadvantages, prior art quick change took holders and drill chucks also tended to be complex, either in structure or in manufacture, necessitating a relatively high cost to the user.